The control of bleeding as well as the sealing of air and various bodily fluids is essential and critical in surgical procedures to minimize blood loss, to seal tissue and organ structures, to reduce post-surgical complications, and to shorten the duration of the surgery in the operating room.
In an effort to provide dressings with enhanced hemostatic and tissue sealing and adhering properties, therapeutic agents, including, but not limited to, thrombin, fibrin and fibrinogen have been combined with dressing carriers or substrates, including gelatin-based carriers, polysaccharide-based carriers, glycolic acid or lactic acid-based carriers and a collagen matrix. Examples of such dressings are disclosed in U.S. Pat. Nos. 6,762,336, 6,733,774 and PCT Publication No. WO 2004/064878 A1.
In order to evaluate the efficacy of dressings with enhanced hemostatic, tissue sealing and adhering properties, it is desirable to quantify the peel adhesion properties of a dressing. Peel adhesion testing is a well established methodology in industrial applications involving tapes, adhesives and the like. It has also been employed to a limited extent in the biomaterials field. Various standard methods for conducting peel tests are available including T-peel, cleavage peel, climbing drum and floating roller techniques.
Although the aforementioned tests have many important industrial uses, they are not particularly well suited when the peel adhesion testing involves the measurement of soft tissue adherence. For this purpose standard techniques present certain disadvantages. For example, the status of the soft tissue/dressing interface may be rather unstable and susceptible to dehydration and other changes, while at the same time the delay between surgical removal of the specimen and the actual conduct of the peel test may be substantial.
Additionally, a variable angle between the peeling force and the substrate in some of the standard tests available today presents a complication from a biomechanical standpoint. Accordingly, it would be desirable to maintain a substantially constant angle throughout the test. Tests carried out heretofore utilizing the winding drum method have produced results having wide variability. In conventional winding drum testing, one aluminum strip of the test specimen is first secured to a rigid bar as a backing and the bar is suspended by one of its ends from an upper tensile-applying point of the test machine. A turned-out end of the other aluminum strip is tucked and attached within a slot of a drum having substantial weight. Flexible bands around the flanges of the drum are brought downward and attached by a yoke to an attachment point in the laboratory floor. The upper tensile-applying point has associated therewith a force registering means.
K. Bundy, in “An Improved Peel Test Method for Measurement of Adhesion to Biomaterials,” Journal of Materials Science: Materials in Medicine, 11 (2000) 517-521, proposes a portable peel-testing instrumentation for testing adherence of soft tissues to biomaterials. It is said to maintain a 900 angle between peel and substrate, simplifying the determination of applied normal forces when separating tissue layers from material surfaces. The instrument has been reported to have been used to test adhesion of tape to a biomaterial surface, assess strength of tissue adhesives and measure adhesion of subcutaneous tissue to orthopedic biomaterials. However, in the method proposed, the tissue is the moving part while the substrate is fixed. As the tissue stretches during testing, error is introduced into the calculation of peel force. In fact, the data presented reveals a rather large variation.
U.S. Pat. No. 2,989,865 proposes an apparatus for testing the peel strength of joints that comprises improvements in the apparatus and method for testing whereby an end of one of two members so joined (usually thin strips of aluminum) is secured to a winding drum and peeled from the other member by winding progressively on the drum, the force required for such peeling being continuously registered.
U.S. Patent Publication No. 2006/0237128 proposes a method of bonding two materials directly with each other, at least one of which is made of a plastic material, which method is applicable to bonding two materials, with no need to use any bonding agent and without allowing the materials to be exposed to high temperature and/or high pressures. In this method in which a first member made of a plastic material and a second member are bonded together, one surface of the first member to be bonded with the second member is irradiated with energy rays having a quantity of energies not lower than 4 eV, followed by directly bonding the first and second members together without any bonding agent being used. A method of conducting a peel strength test at a right angle to determine the adhesive strength is proposed in U.S. Patent Publication No. 2006/0237128.
Despite these advances in the art, there remains a need for an apparatus and method for evaluating the peel adhesion of a test specimen to a substrate.